Expose ImsResolver API that checks ImsService configurations

Exposes an ImsResolver API to check whether or not there is a
configured ImsService for the ImsFeature type requested. This
allows us to check if there is an ImsService available to service
a request from another app and if not, send a unsupported operation
ImsExcpetion.

Bug: 184188331
Test: atest CtsTelephonyTestCases FrameworksTelephonyTestCases
Change-Id: I69b7f73d35bd1bd5049ba9a437907894f22b7e0b